1. Field of the Invention
The invention relates to the field of transmit/receive devices.
The invention particularly relates to transmit/receive devices utilizing a single antenna for both transmit and receive functions.
The invention specifically relates to the field of transmit/receive switches for use in such devices to minimize power consumption required to switch the antenna to the appropriate device, utilizing minimum power consumption in performing said switching operation and in maintaining connection with the appropriate device.
The invention further relates to transmit/receive switches wherein inadvertent switching of the antenna to the nonappropriate transmit/receive device is inhibited.
2. Prior Art
Transmitting and receiving installations require both transmitting and receiving antennas. The transmitting antenna couples the information to be transmitted into the atmosphere. The receiving antenna acts as a collector of energy radiated into the atmosphere by a transmitting device. When the transmitter and receiver are located at the same site it is important that the information being radiated at a high energy level by the transmitter be decoupled from the receiving device lest energy be received by the receiver at a level which might be damaging to the receiver. To this end, the receiving device is frequently disconnected by means of a relay which is activated while the transmitter is operative.
Certain installations utilize a single antenna for both transmit and receive functions. Means must then be provided to properly time share the usage of the antenna by the transmitter and the receiver devices. Such time sharing devices may comprise simple control relay mechanisms or radiated energy activated devices in wave guide systems or the like.
As the art has progressed, it has become possible to produce hand-held transmit/receiver devices denoted generically as transceivers. Limiting the usefulness of such transceiver devices is the power source available for energizing both the transmit and the receive function. The load carrying capacity of a battery is generally reduced in direct proportion to size reduction of the battery. Thus, miniaturization of transceiver devices is, in general, limited to the battery power supply utilized with the device. Trade offs may be made in terms of useful life of the transistor for any given battery size versus range and power handling capabilities of the transceiver also as a function of battery size and capacity. It is therefore desirable that components of transceiver devices be modified wherever possible to reduce or eliminate current drain on the battery supply.
Transceivers frequently employ a relay which in its non-activated state connects the antenna of the transceiver to the receiver device. When the operator wishes to transmit, he initiates a transmit command, usually by operation of a transmit switch, which energizes the antenna relay causing it to switch the antenna from the receiver to the transmitter device within the transceiver. Current must flow to the relay to hold it in its transmit position while the operator is transmitting. This current drain, to maintain the relay energized, limits the power handling capabilities of the transmitter device and decreases the useful working life of the battery power supply. To avoid this current drain, those skilled in the art have replaced such conventional switching relays with latching type relays which need be energized only to initiate a change in state. Once the switch has changed its state it wil hold its switched position without the need for further energization. Thus the current drain required of such a latching relay is less than that normally required for conventional relays.
Latching relays, however, pose other problems. Should the operator disconnect the power from the transceiver while the transceiver was still in the transmit mode, the latching relay would remain in the transmit mode when next the transceiver was powered. Thus, although the operator would not be keying the transmitter device, the antenna would be connected to the transmitter and no energy from a distant source already radiated into the atmosphere would be able to be received by the transceiver in this condition. A similar result might well obtain should the transceiver suffer a shocking jar causing the latching relay contacts to move from the receive position to the transmit position. Again, the antenna relay would be in a non-operative position. When the operator established a command to switch the transceiver to the transmit function, the relay would be activated so as to connect the antenna to the receiver. In this instance, no energy would be radiated into the atmosphere from the transceiver. The possibility of a latching relay assuming such ambiguous positions is seen to be highly undesirable.
An additional problem concerns changing of the operating mode of the transceiver by the operator before the latching relay has achieved a steady state condition. A prescribed time interval, during which power must be applied to the relay coil, is required for the transition of the contacts from one position to another. If the operator were to command the transceiver initially to the transmit function and then re-command it to the receive function before the initial command had been completed, simultaneous energization of the relay coils would result which could damage the relay. Even if damage would not occur, the eventual final state of the relay contacts would be unknown and ambiguity in the relay state results.
It is an objective of the present invention to provide a transmit/receive switch which will require minimal current drain from the transceiver power supply in order to achieve proper functioning of the switch.
It is a particular objective of the invention to provide a transmit/receive switch having provision to automatically inhibit ambiguous positioning of the switch contacts.
It is a specific objective of the invention to provide a transmit/receive switch utilizing a feedback control circuit in conjunction with a latching relay so as to provide unambiguous, low loss, voltage-controlled connection of a common antenna to either a transmitter or receiving device within a transceiver which transmit/receive switch requires no steady state relay operating power.
It is a further objective of the invention to utilize logic circuitry in hybrid form to provide a transmit/receive switch of extremely small size.